Abstract: The concept of image walls as a counterpart of the well known image source concept is introduced and applied to the calculation of traffic noise levels under reverberant conditions like in a long linear street tunnel or in urban streets. According to this concept a traffic stream of equally spaced vehicles with identical acoustic power output is equivalent to just one source situated between a pair of rigid image walls. This pair of walls, together with the tunnel's boundaries form an enclosure for which the classical formulae frorm room acoustics may be used for calculating the reverberant traffic noise sound pressure levels. Two application examples are given and compared with measured data.